1. Field of the Invention
This invention relates to a method, device, and recording medium for output control and duplication prevention control using, for example, an anti-duplication control signal recorded in a recording medium together with an information signal.
2. Description of Related Art
VTR (Video Tape recording devices) has been popularized in daily life, and many kinds of software which can be played back on a VTR are supplied abundantly. Digital VTR or DVD (Digital Video Disks) playback devices have been available commercially now, and provide images and sound of exceptionally high quality.
On the other hand, there is, however, a problem in that software applications of this great abundance can be copied without restriction, and several methods have already been proposed to inhibit duplication.
For example, though the method is a method which inhibits duplication of an analog video signal not directly, one method to prevent copying uses a difference in the AGC (Automatic Gain Control) system, or in the APC (Automatic Phase Control) system, for example, between the VTR recording device and a monitor receiver for displaying the image.
For example, the method which utilizes the difference in AGC system, in which a VTR performs AGC using a pseudo sync signal inserted in the video signal and a monitor receiver employs a different AGC system not using the pseudo sync signal, is an example of the former. In detail, when an analog video signal is recorded in an original recording medium, a very high level pseudo sync signal is previously inserted as a sync signal for AGC, and the very high level pseudo sync signal is inserted in the video signal to be supplied from a playback VTR to a recording VTR as a sync signal for AGC.
Alternately, the method which utilizes the difference of APC characteristics between a VTR and receiver as in the case that APC in a VTR can follow the color burst signal in a video signal with a short time constant but APC in a receiver follows with a relatively long time constant is an example of the latter. In detail, the phase of the color burst signal of a video signal is previously inverted partially when the analog video signal is recorded in an original recording medium, and the color burst signal having partially inverted phase is output as a video signal to be supplied from a playback VTR to a recording VTR.
As the result, the monitor receiver which receives the analog video signal from the playback VTR plays back the image correctly without being affected by the pseudo sync signal in AGC or without undesirable effects of the partial phase inversion of the color burst signal used for APC.
On the other hand, in a VTR, which is supplied with the analog video signal from the playback VTR into which pseudo sync signals have been inserted or which has been subjected to color burst signal phase inversion control as described herein above, for receiving such analog video signal and for recording the analog video signal in a recording medium, proper gain control or phase control based on the input signal cannot be performed, and so the video signal is not correctly recorded. Even if this signal is played back, therefore, normal picture and sound cannot be obtained.
As described herein above, in the case that involves an analog video signal, the method does not directly inhibit duplication but is a method for causing an abnormally played back picture which can not be viewed normally. Such prevention method is a passive duplication prevention control.
On the other hand, in the case that a digitized information, for example, a video signal is involved, an anti-duplication signal or an anti-duplication control signal comprising, for example, a duplication ranking control code, is added as digital data to the video signal and recorded on the recording medium, so as to prevent or control duplication of the image.
FIG. 1 is a basic structural diagram of a duplication apparatus for duplicating digitized information, a digital information played back by the digital playback device 110 is sent to a digital recording device 120 through a digital transmission line 120, and the digital recording device 101 duplicates the digital information if duplication is permitted and does not duplicate the digital information if duplication is not permitted.
An anti-duplication control information in the form of additional information is recorded in a recording medium 111 placed on the digital playback device 110 in addition to a digital main information. The anti-duplication control information indicates control content such as duplication inhibition, duplication permission, or generation restriction. The digital playback section 112 reads out the information from the recording medium 111, acquires the anti-duplication control information together with the digital main informational and sends them to the digital recording device 120 through the digital transmission line 101.
An anti-duplication control signal detection section 122 of the digital recording device 120 detects the anti-duplication control signal out of the information received from the digital transmission line 101, and judges the control content. The judgement result is sent to a digital recording section 121.
If the judgement result of the anti-duplication control signal from the anti-duplication control signal detection section 122 indicates permission of recording of the digital information input through the digital transmission line 101, then the digital recording section 121 converts the input digital signal to a digital information suitable for recording, and writes it in the recording medium 123, that is, recording is performed. On the other hand, if the judgement result of the anti-duplication control signal from the anti-duplication control signal detection section 122 indicates duplication inhibition, then the digital recording section 121 does not perform recording processing of the input digital information.
Further, if the judgement result of the anti-duplication control signal from the anti-duplication control signal detection section 122 indicates permission of recording of only the first generation, then the digital recording section 121 converts the input digital signal to a digital information suitable for recording, and writes it in the recording medium 123, that is, recording is performed, and additionally, converts the anti-duplication control signal in the form of additional information to a signal for indicating duplication inhibition (duplication inhibition of next generation), and records it in the recording medium 123. Therefore, the video signal can not be duplicated further using the recording medium 123 in which the duplicated information is recorded.
As described herein above, in the case of digital connection that the main information signal and anti-duplication control signal added as an additional information are supplied to a recording device in the form of digital signal, because the anti-duplication control signal is contained in the digital data to be transmitted, duplication prevention control such as duplication inhibition is performed consistently in a recording device using the anti-duplication control signal.
In the case of a duplication prevention control method in which the above-mentioned difference in AGC system or the difference in APC characteristics between a VTR and monitor receiver is used, a pseudo sync signal is inserted in the video signal recorded in a recording medium or the phase of color burst signal is inverted partially. In other word, this method involves processing as described herein above on the sync signal portion, hence a video signal which provides a normal image can undesirably be duplicated after the sync signal is changed. The duplicated video signal can be duplicated repeatedly.
In the case of a duplication prevention control method utilizing the difference in AGC system or the difference in APC characteristics between a VTR and monitor receiver, a video signal is undesirably recorded normally depending on the AGC system or APC characteristics of the recording device side, and a video signal can be duplicated even without changing sync signal portion. As described herein above, it can happen that even such passive duplication prevention does not work.
In the case of a device which involves the digitized video signal described herein above using FIG. 1, if the position where an anti-duplication control signal is recorded is recognized, then it is possible to duplicate the video signal by changing the portion where the anti-duplication control signal is recorded or by removing the anti-duplication control signal.
In the case that the digital playback device in FIG. 1 is, for example, a digital VTR, in order to monitor the played back video signal and audio signal, both the video signal, that is the main information signal, and the audio signal are converted to an analog signal through a D/A conversion circuit 113 and guided to an analog output terminal 114 connected usually to a monitor receiver.
As described herein above, though the playback device is a device for playing back digital signals, the anti-duplication control signal is not contained in the analog signal guided to the analog output terminal 114. Therefore, in the case of analog connection that an analog device such as analog VTR is connected to the analog output terminal 114, duplication of the information signal is undesirably possible.
As described herein above, on the video signal from which an anti-duplication signal added originally on the video signal is removed and which is duplicated thereafter in a recording medium, there is no anti-duplication control signal. It is not required to remove an anti-duplication control signal for duplication, hence, the video signal which is duplicated illegally can be played back or duplicated without restriction. In this case, illegal duplication can be operated more easily.
Further, in the case that a recording medium in which an illegally duplicated video signal is recorded is used, the image is played back normally. Therefore, a user can not recognize whether the video signal recorded in the recording medium is a video signal recorded illegally or not illegally. Hence, if the video signal recorded in the recording medium is a video signal duplicated illegally, users do not complain to a supplier who duplicated and supplied the video signal illegally about the video signal unless the quality of the played back image is very poor, as the result, illegally duplicated video signals become abundant.
In view of the above-mentioned problem, it is the object of the present invention to provide a method, device, and recording medium for preventing illegal duplication of information signals such as video signals and preventing use of video signals duplicated illegally in order to eliminate the above-mentioned problem.
To solve the above-mentioned problem, the information signal output control method in accordance with the present invention involves a method in which a plurality of anti-duplication control signals of different types generated correlatively to each other added on the information signal is detected, and the output control of the information signal is performed dependently on detection condition of the plurality of anti-duplication control signals of different types.
In the information signal output control method in accordance with the present invention, a notice information is output if a specific anti-duplication control signal out of the plurality of anti-duplication control signals of different types generated correlatively to each other added on the information signal is missed and playback output of the information signal is not output.
In the information signal output control method in accordance with the present invention, one of the plurality of anti-duplication control signals of different types generated correlatively to each other is a spectrally spread anti-duplication control signal added on the information signal.
The information signal duplication prevention method in accordance with the present invention involves a method in which when an information signal is duplicated, the information signal on which the plurality of anti-duplication control signals of different types generated correlatively to each other is added is duplicated.
In the information signal duplication prevention method in accordance with the present invention, one of the plurality of anti-duplication control signals of different types generated correlatively to each other is a spectrally spread anti-duplication control signal superimposed on the information signal.
In the information signal duplication prevention method in accordance with the present invention, in the case that the plurality of anti-duplication control signals of different types added on the information signal is detected and at least any one of the plurality of anti-duplication control signals of different types added on the information signal is missed, a notice information is output.
According to the information signal output control method in accordance with the present invention, the output control of an information signal is performed dependently on detection condition of a plurality of anti-duplication control signals generated correlatively to each other added on the information signal.
For example, if all the plurality of anti-duplication control signals added on the video signal is detected or all the anti-duplication control signals are not detected, the information signal is judged to be a legally duplicated information signal and the video signal is output.
On the other hand, if, for example, the anti-duplication control signal which should be added without exception out of a plurality of anti-duplication control signals which should be added on the information signals is not detected, the information signal is judged to be an information signal from which the above-mentioned anti-duplication control signal is removed probably for the purpose of illegal duplication, and the information signal is controlled so as not to be output.
Hence, the illegally duplicated information signal is not used. Users will complain to the supplier who has supplied the illegally duplicated information signal that the information signals can not be used, the complaint lets the supplier recognize that the information signal can not be illegally duplicated, and thus illegal duplication of the information signal is prevented.
According to the information signal output control method in accordance with the present invention, if, for example, the specific anti-duplication control signal which should be added without exception out of a plurality of anti-duplication control signals which should be added on the information signal is missed, the information signal is not output, and a notice message for indicating that this information signal is an illegally duplicated information signal is output instead.
Hence, the user can recognize clearly that the information signal to be output if it is normal is not output not due to failure of the device f or outputting the information signal, but due to illegal duplication.
According to the information signal output control method in accordance with the present invention, one of a plurality of anti-duplication control signals of different types added on the information signal is an anti-duplication control signal spectrally spread and added on the information signal.
Because the spectrally spread anti-duplication control signal is added on the information signal as a wide-band low-level spectral spread signal, it is difficult to remove it intentionally. Therefore, the spectrally spread anti-duplication control signal remains consistently on the information signal, the spectrally spread anti-duplication control signal exists, hence, if other anti-duplication control signals which should be contained in the sync signal are not detected due to changing of sync signal, then the information signal is judged clearly to be an illegally duplicated information signal.
According to the information signal duplication prevention method in accordance with the present invention, in the case that duplication of the information signal is performed, a plurality of anti-duplication control signals of different types having the correlative relation that as long as the one anti-duplication control signal exists then the other anti-duplication control signal also exists with out exception is added on the information signal and the information signal is duplicated.
By adding a plurality of anti-duplication control signals of different types with correlative generation on the information signal and by recording the information signal in a recording medium, if at least one of the plurality of anti-duplication control signals added on the information signal is missed, the information signal is judged easily to be an illegally duplicated information signal.
According to the information signal duplication prevention method in accordance with the present invention, one of the plurality of anti-duplication control signals of different types to be added on the information signal to be recorded is spectrally spread and then added on the information signal.
As described herein above, it is difficult to remove an anti-duplication control signal intentionally because the spectrally spread anti-duplication control signal is added on the information signal as a wide-band low-level spectral spread signal. Hence, if an illegally duplicated information signal contains the one spectrally spread anti-duplication control signal and the other anti-duplication control signal is not detected, this information signal is judged clearly to be an illegally duplicated information signal.
According to the information signal duplication prevention method in accordance with the present invention, if at least any one of the plurality of anti-duplication control signals of different types which should be added normally on the information signal is missed, a notice information is output.
Thereby, a user can recognize that the information signal which wanted to be duplicated is an illegally duplicated information signal.